1. Field of the Invention
The present invention relates to a method of producing silicon carbide that is capable of producing high-purity silicon carbide simply and at a high degree of productivity using a silicone composition.
2. Description of the Prior Art
Silicon carbide ceramics are chemically stable at both normal temperatures and high temperatures, and exhibit excellent mechanical strength at high temperature, and are therefore widely used as high-temperature materials. In recent years, in the field of semiconductor production, high-purity silicon carbide ceramic sintered bodies, which exhibit excellent heat resistance and creep resistance, have started to be used as boards and process tubes and the like within steps for conducting wafer heat treatments or the thermal diffusion of trace elements. If the silicon carbide material used in these steps comprises impurity elements, then these impurity elements may become incorporated within the wafer during heating of the wafer, causing contamination of the wafer. Accordingly, the silicon carbide material used in these applications should preferably have as high a degree of purity as possible.
Known methods of producing silicon carbide powder include the Acheson process, silica reduction methods, and vapor phase reaction methods. However, silicon carbide produced using the Acheson process tends to suffer from low purity, silica reduction methods suffer from problems of uniformity resulting from heterogeneous mixing of the silica powder and the silicon carbide powder, and vapor phase methods suffer from problems of low productivity. Recently, a method that uses a silicon metal alloy as the starting raw material has been reported (see Patent Document 1), and although this method enables silicon carbide to be obtained at low temperatures, the steps are complex, including conducting reaction under high pressure. Further, methods of generating carbon-silicon bonds by mixing an ethyl silicate containing no carbon-silicon bonds with an organic compound, and then heating and reacting the mixture have also been reported (see Patent Documents 2 and 3), but the large quantity of decomposition products generated means it is difficult to claim that these methods offer a high degree of productivity.
Furthermore, because silicon carbide is usually resistant to sintering, conventionally, obtaining a silicon carbide molded item having a desired shape and dimensions is far from simple.    [Patent Document 1] US 2006/0171873 A1    [Patent Document 2] JP 11-171647 A    [Patent Document 3] JP 2006-256937 A